Tuberculosis: A Comprehensive Overview
Introduction
Tuberculosis (TB) is one of the world’s oldest and most persistent infectious diseases, caused by the bacterium Mycobacterium tuberculosis. Despite advances in medicine, TB remains a major global health concern, particularly in developing countries. According to the World Health Organization (WHO), TB is one of the top 10 causes of death worldwide and the leading cause from a single infectious agent, surpassing HIV/AIDS. The disease primarily affects the lungs (pulmonary TB) but can also involve other organs (extrapulmonary TB). TB is preventable and curable, yet its burden continues due to poverty, inadequate healthcare, drug resistance, and co-infection with HIV.
Causes and Transmission
The causative agent of TB is Mycobacterium tuberculosis, a slow-growing, aerobic, acid-fast bacillus. The bacteria spread from person to person through airborne droplets when an infected individual coughs, sneezes, or talks.
- Inhalation of droplets is the primary route of transmission.
- Only people with active pulmonary TB are contagious.
- A single sneeze can release thousands of infectious particles.
Most individuals exposed to TB bacteria do not develop the disease immediately. Instead, the bacteria may remain dormant in the body, leading to latent TB infection. People with latent TB are asymptomatic and non-contagious but can develop active TB if their immune system weakens.
Risk Factors
Several factors increase the risk of developing active TB:
- HIV/AIDS infection – weakens the immune system, greatly increasing susceptibility.
- Malnutrition – compromises immunity.
- Diabetes mellitus – doubles the risk of active TB.
- Close contact with a TB patient.
- Living conditions – overcrowded, poorly ventilated settings (e.g., prisons, shelters).
- Substance abuse – smoking, alcohol, and drug use increase vulnerability.
- Weakened immunity – due to cancer, chronic kidney disease, or immunosuppressive therapy.
Signs and Symptoms
TB can affect multiple organs, but the clinical presentation varies:
Pulmonary TB (most common form):
- Persistent cough lasting more than 2 weeks
- Chest pain
- Coughing up blood (hemoptysis)
- Shortness of breath
- Fatigue and weakness
- Night sweats
- Fever and chills
- Loss of appetite and weight loss (“consumption” was an old term for TB due to this wasting effect)
Extrapulmonary TB (affecting other organs):
- Lymph nodes: painless swelling
- Bones and joints: pain, deformity, restricted movement
- Kidneys: blood in urine
- Meninges (TB meningitis): headache, stiff neck, altered consciousness
- Gastrointestinal system: abdominal pain, diarrhea, malabsorption
Diagnosis
Timely diagnosis is critical for treatment and prevention of TB transmission. Common diagnostic methods include:
- Medical history and physical examination – assessment of symptoms and risk factors.
- Sputum microscopy and culture – detecting acid-fast bacilli.
- Molecular tests (GeneXpert MTB/RIF) – rapid detection of TB and rifampicin resistance.
- Tuberculin skin test (Mantoux test) – indicates prior exposure to TB bacteria.
- Interferon-Gamma Release Assays (IGRAs) – blood tests for latent TB infection.
- Chest X-ray – identifies lung damage typical of TB.
- CT scans and MRI – helpful in extrapulmonary TB.
Treatment
Treatment for TB involves prolonged use of antibiotics to ensure eradication of the bacteria. The standard regimen is known as Directly Observed Treatment, Short-course (DOTS):
- First-line drugs:
- Isoniazid (INH)
- Rifampicin (RIF)
- Pyrazinamide (PZA)
- Ethambutol (EMB)
The typical course lasts 6 months:
- Intensive phase (2 months): INH, RIF, PZA, EMB
- Continuation phase (4 months): INH and RIF
Drug-Resistant TB
Drug resistance is a growing challenge:
- MDR-TB (Multidrug-Resistant TB): resistant to INH and RIF.
- XDR-TB (Extensively Drug-Resistant TB): resistant to first-line drugs and some second-line drugs.
Treatment for drug-resistant TB is longer, more toxic, and less effective, requiring newer agents such as bedaquiline, delamanid, and linezolid.
Prevention
Prevention strategies are vital to controlling TB:
- Vaccination: The Bacillus Calmette–Guérin (BCG) vaccine provides partial protection, especially in children against severe TB forms like meningitis.
- Infection control: Adequate ventilation, cough etiquette, use of masks, and early treatment of active TB cases.
- Screening and prophylaxis: High-risk individuals, especially HIV-positive patients, should undergo screening and may be given preventive therapy.
- Improved living conditions: Reducing overcrowding and malnutrition decreases TB spread.
Global Burden
- Around 10 million people fall ill with TB annually.
- Nearly 1.3 million deaths occur each year, making it a leading cause of infectious mortality.
- TB disproportionately affects low- and middle-income countries, with Asia and Africa carrying the highest burden.
- The COVID-19 pandemic disrupted TB services, leading to an increase in missed diagnoses and deaths.
Complications
If untreated or poorly managed, TB can cause:
- Lung destruction and respiratory failure
- Massive hemoptysis (life-threatening bleeding)
- Spread to multiple organs (miliary TB)
- Chronic pain and disability in bone/joint TB
- Neurological damage in TB meningitis
Conclusion
Tuberculosis remains a global health challenge despite being preventable and curable. The disease thrives in conditions of poverty, undernutrition, and weak healthcare systems. Effective strategies, including early detection, appropriate treatment, vaccination, and social interventions, are essential to reduce its burden. Continued global commitment is needed to achieve the WHO’s “End TB Strategy,” which aims to eliminate TB as a public health problem.
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